Draw-form for exhaust components and method of manufacture

ABSTRACT

Exhaust tubes comprise tubular structures having draw-forms formed therein so as to provide a flat portion where a HEGO boss (Heated Exhaust Gas Oxygen) can be welded for placement of the HEGO sensor. In such circumstances, it is, therefore, useful that such draw-forms have substantially flat portions. The present invention provides a tubular member having an outer wall, and a draw-form formed in the outer wall. The draw-form comprises a substantially flat bottom portion, a plurality of walls extending upwardly from the bottom portion and attached to the outer wall, and wherein the walls are configured in a polygonal orientation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application No. 60/589,111 filed on Jul. 19, 2004, which is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention is generally related to exhaust tubes, and more particularly to exhaust tubes having a draw-form formed therein.

BACKGROUND

Many tubular structures designed to have components connected thereto. In such a case, many tubular structures utilize flat portions formed along the surface of the tubular structure for mounting components thereto. While such flat portions assist in mounting components to tubes, these flat portions can often be deformed during secondary forming operations or construction of the finished product. The deformation of such flat portions can prevent the connection of the required component and require additional forming operations to correct such deformations.

The field of art has attempted to minimize the deformation to the flat portions caused by secondary operations by providing circular draw-forms having a flat portion therein (as shown in FIG. A). The circular draw-forms are stamped into the tubular surface so as to provide a flat portion upon which a component may be mounted. As such, the wall of the circular indentations is supposed to protect the flat portion from deforming during secondary forming or construction operations.

One particular industry where tubular structures require such flat portions is the automotive industry and particularly the exhaust tube industry. For example, tubular catalytic converter canisters comprise tubular structures having draw-forms stamped therein so as to provide a flat portion where a HEGO boss (Heated Exhaust Gas Oxygen) can be welded for placement of the HEGO sensor. This sensor is used by the engine management system to monitor mixture strength in the exhaust gases. In construction of such canisters, a circular draw-form indentation is typically stamped into the tubular structure so as to provide a flat surface for the HEGO boss. Converter bricks are then stuffed inside the tube and the entire assembly is swaged, or reduced to a smaller diameter, in a secondary operation. The forming forces during swaging tend to deform the flat portion and the attached HEGO boss under the current forming methods (as shown in FIGS. 1 and 2).

It has been observed that circular shaped draw-forms tend to deform during subsequent forming operations. Deformation of the draw-forms and their flat portions can inhibit the connection of the HEGO sensor and make the tube worthless for its intended purpose. Such deformation of the draw-form and flat portion must be repaired or reformed in subsequent operations to permit the proper connection of the HEGO sensor. Such corrective action can be time consuming and costly. Therefore, there is a need in the art to prevent the current occurrence of deformation found in circular draw-forms during subsequent forming operations.

Therefore, there is a need in the art to provide a draw-form and a method for producing a draw-form in a tubular structure that either does not deform, or minimally deforms, so as to maintain the required flat portion needed for the proper connection of components.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a tubular member having an outer wall, and a draw-form formed in the outer wall. The draw-form comprises a substantially flat bottom portion, a plurality of walls extending upwardly from the bottom portion and attached to the outer wall, and wherein the walls are configured in a polygonal orientation.

In an alternative embodiment, the present invention provides an exhaust tube that comprises a tube having an outer wall defining an interior exhaust passage, a draw-form formed in the outer wall. The draw-form comprises a substantially flat bottom portion, a plurality of walls extending upwardly from the bottom portion and integrally attached to the outer wall, and wherein the walls are configured in a polygonal orientation to substantially prevent deformation of the draw-form during subsequent forming operations.

In yet another embodiment, the present invention provides a method of manufacturing a draw-form. The method comprises placing a tubular member having an outer wall in a fixture, forming a substantially flat bottom portion in the outer wall of the tube, forming a plurality of walls extending upwardly from the bottom portion and attached to the outer wall, wherein the walls are configured in a polygonal orientation to maintain the bottom portion substantially free from deformation during subsequent forming operations.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

DESCRIPTION OF THE DRAWINGS

Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustrations, wherein:

FIG. A is a top view of a tubular member having a previously known circular draw-form therein;

FIG. 1 is a top view of a tubular member having a previously known circular draw-form and HEGO boss showing deformation thereof after a secondary forming operation;

FIG. 2 is an interior view of FIG. 1;

FIG. 3 is a perspective view of a tubular member having a draw-form according to the present invention.

FIG. 4 is an interior view of FIG. 3;

FIG. 5 is a close-up view of the draw-form shown in FIG. 3;

FIG. 6 is a cross-sectional view and close-up thereof of a tubular member having a draw-form with a MIG welded HEGO boss connected thereto; and

FIG. 7 is a cross-sectional view and close-up thereof of a tubular member having a draw-form with HEGO boss CD welded thereto, which is the most preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention is described with reference to the preferred embodiment, it should be clear that the present invention could be used with any tubular structure in any industry where tubular structures require flat connection portions. Therefore, the description of the preferred embodiment herein in illustrative of the present invention and should not limit the scope of the invention.

With reference to FIGS. 3-5, a draw-form 10 is formed in a tubular member or tube 12. The tube 12 can be made from any material that permits formation of the draw-form 10, and is preferably composed of metal material. The tube 12 includes an outer wall 11 that defines an interior exhaust passage 13. The draw-form 10 comprises a substantially flat bottom portion 14 having an aperture 16 extending therethrough and bounded by walls 18 configured in a polygonal orientation. The walls 18 may be substantially parallel to said bottom portion 14, but may also be at a non-right angle thereto, such as an acute or obtuse angle. Additionally, the walls 18 are attached to the outer wall 11 of the tube 12. They may be attached integrally. Additionally, the walls 18 may be attached to the bottom portion 14 either integrally or non-integrally. To non-integrally attach the bottom portion 14 to the walls 18, the bottom portion 14 is welded in place. Otherwise, if the walls 18 are integrally formed with the bottom portion 14, the two are created during a forming operation such as stamping.

Preferably, the walls 18 are configured to form a rectangular or square configuration, however, other polygonal orientations may be used. The straight-line walls 18, which may have rounded corners, act as strengthening ridges that prevent the deformation of the draw-form 10 during subsequent forming operations, such as swaging, so as to maintain the flat portion 14 substantially free from deformation. As such, the polygonal draw-form 10 restricts the movement of tubing material in the area where the draw-form 10 exists and maintains the flat portion 14 in generally its stamped configuration. In other words, the polygonal draw-form 10 prevents large displacements in the formed area during a secondary post draw-form operation.

In the method of manufacture, the tube 12 is placed with a draw-form press (not shown). A properly configured polygonal male punch is used in conjunction with a corresponding polygonal female die to make the desired polygonal draw-form 10 at the desired draw depth in the tube 12. As indicated above, the draw-form 10 can be any polygonal figure, but preferably the draw-form is either rectangular or square.

Once the draw-form 10 has been formed in the tube 12, the HEGO boss can be mounted to the draw-form 10. As shown in FIG. 6, the traditional method of mounting a HEGO boss 20 to the draw-form 10 is by MIG welding, although any welding process can be utilized. The HEGO boss 20 is inserted within the aperture 16 and connected by welds 22 therein. As shown in FIG. 7, the preferred embodiment, the HEGO boss 20 is CD welded (capacitive discharge) to the interior of the draw-form 10. In FIG. 7, the HEGO boss 20 includes protrusions 30 thereon that assist in attaching it to the draw-form 10. The protrusions 30 can be used to temporarily attach the HEGO boss 20 to the bottom portion 14 of the draw-from 10 until it is welded in place. Alternatively, the protrusions 30 can be used to attach the HEGO boss 20 directly to the bottom portion 14. Additionally, the HEGO boss 20 may be attached to the underside of the bottom portion 14 of the draw-form 10, as shown in FIG. 7, or it may be attached to the top side of the bottom portion 14.

The present polygonal draw-form displays strength characteristics superior to the prior used circular draw-forms during secondary forming operations. As opposed to the circular draw-forms, the angular orientation of the straight-lined walls 18 withstands and better distributes the forces acting thereon during the secondary forming operation.

The invention has been described above and, obviously, modifications and alternations will occur to others upon a reading and understanding of this specification. The claims as follows are intended to include all modifications and alterations insofar as they come within the scope of the claims or the equivalent thereof. 

1. A tubular member comprising: an outer wall; and a draw-form formed in said outer wall, said draw-form comprising: a substantially flat bottom portion; a plurality of walls extending upwardly from said bottom portion and attached to said outer wall; and wherein said walls are configured in a polygonal orientation.
 2. The tubular member of claim 1, wherein said draw-form further includes an aperture extending through said bottom portion.
 3. The tubular member of claim 2, wherein said walls have substantially rounded corners.
 4. The tubular member of claim 3, wherein said walls are integrally formed with said bottom potion.
 5. The tubular member of claim 4, wherein said polygonal configuration is a rectangular configuration.
 6. The tubular member of claim 4, wherein said polygonal configuration is a square configuration.
 7. The tubular member of claim 3, wherein polygonal configuration of said walls substantially prevent deformation of said draw-form during subsequent forming operations.
 8. The tubular member of claim 7, wherein said bottom portion remains substantially free from deformation during subsequent forming operations.
 9. The tubular member of claim 7, wherein said subsequent forming operations includes swaging said tubular member.
 10. The tubular member of claim 1, wherein said walls are substantially perpendicular to said bottom portion.
 11. An exhaust tube comprising: a tube having an outer wall defining an interior exhaust passage; a draw-form formed in said outer wall, said draw-form comprising: a substantially flat bottom portion; a plurality of walls extending upwardly from said bottom portion and integrally attached to said outer wall; and wherein said walls are configured in a polygonal orientation to substantially prevent deformation of said draw-form during subsequent forming operations.
 12. The exhaust tube of claim 11, further including an aperture extending through said bottom portion.
 13. The exhaust tube of claim 12, wherein said walls have substantially rounded corners.
 14. The exhaust tube of claim 13, wherein said polygonal configuration is a rectangular configuration.
 15. The exhaust tube of claim 13, wherein said polygonal configuration is a square configuration.
 16. The exhaust tube of claim 13, wherein said rounded corners act as strengthening ridges.
 17. The exhaust tube of claim 16, wherein said bottom portion remains substantially free from deformation during subsequent forming operations.
 18. The exhaust tube of claim 17, further comprising a heated exhaust gas oxygen boss inserted into said draw-form, wherein said heated exhaust gas oxygen boss includes projections for assisting in attaching said heated exhaust gas oxygen boss to said draw-form.
 19. The exhaust tube of claim 18, further comprising a heated exhaust gas oxygen sensor inserted into said heated exhaust gas oxygen boss.
 20. The exhaust tube of claim 19, wherein said subsequent forming operations includes swaging said tubular member.
 21. A method of manufacturing a draw-form, said method comprising: placing a tubular member having an outer wall in a fixture; forming a substantially flat bottom portion in said outer wall of said tube; forming a plurality of walls extending upwardly from said bottom portion and attached to said outer wall, wherein said walls are configured in a polygonal orientation to maintain said bottom portion substantially free from deformation during subsequent forming operations.
 22. The method of claim 21, further comprising swaging said tube wherein deformation of said draw-form is substantially prevented.
 23. The method of claim 22, wherein said walls have rounded corners that act as strengthening ridges.
 24. The method of claim 23, wherein said polygonal configuration comprises a rectangular configuration.
 25. The method of claim 23, wherein said polygonal configuration comprises a square configuration.
 26. The method of claim 25, wherein forming said substantially flat bottom portion is formed by a stamp.
 27. The method of claim 26, wherein said substantially flat bottom portion, said walls, and said aperture are formed by a single operation. 